Methacrylamide monomers have been used in a variety of adhesive compositions, including for orthopedic and dental uses. Dental adhesives are widely used in restorative dentistry to provide retention of the filling materials, creating a bond between the dental material and the hard tissues in the tooth, dentin and enamel. For its application, an acidic etching of the tooth surface creates micropores filled with a mixture of acrylic and/or methacrylic monomers, a photo-initiator system and solvent. The addition of inorganic particles that modulate and improve physical and mechanical properties is also becoming increasingly common. Depending on whether the acidic conditioning of the tooth is done with an acid or with an acidic monomer, the adhesive is classified as “etch & rinse” or “self-etching”.
2-hydroxyethyl methacrylate (HEMA) is one of the most ubiquitous monomers in dental adhesive systems due to its ability to dissolve other higher molecular weight crosslinking monomers, such as bisphenol A glycidyl dimethacrylate (Bis-GMA) or urethane dimethacrylates (UDMA). However, HEMA's hydrophilicity promotes hydrolytic degradation of the polymer network, since the ester bonds of methacrylates hydrolyze under acidic aqueous conditions. In addition, they are known to have allergenic potential and have a considerable level of cytotoxicity. For these reasons, the development of alternatives to its use has been the subject of numerous studies.